The bottom option is for the Admin Centers, click this option then choose ExchangeOnce loaded the page should look similar too:

Now click on Mail Flow from the left-hand menu

This will load the Mail Flow options. The first options will be for rules. If there is a rule called “Black Pearl Mail” or something similar just untick the rule and within 20 minutes emails will no longer go via Black Pearl Mail now proceed to step 8. If there is not a rule then jump to step 5.

If you do not have a rule click on Connectors on the right-hand side:

Then click once on the connector that has Black Pearl Mail in the name(or something similar)

The right-hand side option will change and underneath status, there is a “Turn it off” option, click the option and within 20 minutes emails will no longer go via Black Pearl Mail.